1. Field of Invention
This invention relates to light emitting diode (LED) devices and more specifically, to an improved LED lens and heat sink stem for emitting a spherical light pattern and dissipating heat.
2. Description of Related Art
All light sources convert electrical energy into radiant energy and heat in various proportions. Light emitting diode (LED) devices generate little or no IR (infrared) or UV (ultraviolet) light, but convert only 15% to 25% of the electrical power to visible light, the remainder is converted to heat that must be conducted from the LED die to an underlying circuit board, heat sink, etc.
In order to maintain a low junction temperature to keep good performance of an LED, heat generated by the LED must be dissipated. A build up of heat inside the LED device leads to color shift, reduced light output, shortened life and ultimately device failure. In addition, drive current, thermal path and ambient temperature also affects the junction temperature. Furthermore, high-flux LEDs, which are needed for conventional light illumination, require higher drive currents which further increases junction temperature.
FIG. 1 illustrates a sectional view of a conventional 360 degree lighting angle LED 100 having one or more LED dies 101 which sits atop the first electrode 104. A bonding wire 102 connects the LED die 101 to the second electrode 103. Light emitted by the LED die 101 exits the transparent encapsulate 105 in all directions. The upper surface 106 acts as a partial reflector, reflecting some of the light downwards. In another 360 degree LED prior art example, the encapsulate 105, takes the shape of a sphere 107.
If such LED devices are to be used as conventional lighting, then high-flux LEDs must be incorporated. High-flux LEDs produce more heat, and heat must be moved away from the die 101 in order to maintain expected light output, life and color. Unfortunately, the prior art example contains a critical flaw; it neglects to address LED thermal management; as it does not contain any significant heat sink to draw out the heat via conduction. Electrodes 103 and 104 may draw out some heat; though the majority of the heat generated is trapped inside by the insulating plastic resin encapsulate 105 or 107. Such LED lamps are thus relegated for use with only lower flux LEDs, which would not be suitable for conventional lighting needs. Retrofitting this LED lamp with a sufficient heat sink, beneath the LED die 101 would revert the 360 degree lighting angle back to typical 30 to 140 degree lighting angles.
A need therefore exists for an LED device designed to emit a spherical light pattern while successfully managing the heat generated. Such a device would be advantageous for use as a replacement to current conventional light sources or other applications where spherical light patterns are desired.